Microsoft is reporting yet another zero-day exploit of Internet Explorer 8. The company issued a security advisory Friday confirming the exploit in IE 8 and assuring customers that versions 10, 9, 7 and 6 are not affected.

"This is a remote code execution vulnerability. The vulnerability exists in the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated," Microsoft wrote.

"The vulnerability may corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user within Internet Explorer. An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the Web site," Microsoft said. "Unfortunately, this appears to have already happened."

A Key-Logging Trojan

David Britton, vice president of Industry Solutions at 41st Parameter, told us the latest zero day is yet another standard key-logging Trojan. The Trojan aims to capture data the user is entering and typically zeroing in on log in credentials. The data is then transmitted back to a machine, where it can be used by the attackers to gain access to the compromised accounts.

"We believe that anti-virus measures are critical to put in place to ensure that these types of malware are detected and removed from the client systems," Britton said. "However, due to the fact that new variants can be introduced on an ongoing basis -- and due to the fact that anti-virus is by definition a reactive measure -- we also believe that organizations must put additional layers in place to detect the unauthorized use of credentials by a rogue device."

Prepare for Zero Days

Alex Horan, senior product manager at Core Security, said networks and strategies should be designed based on the assumption that zero-days always exist.

"While you should build defensive technologies into your users' machines, you should also assume at least one user will be compromised and implement a network design and technology that will alert you when a user's machine starts acting in a way that indicates it has been compromised," Horan told us.

Horan insists that a good patch management policy and good security design with containment built-in should help you avoid panic. With these policies and designs in place, he said, you can trust your containment to restrict a breach, your post-breach policies and procedures to effectively identify and scope of the breach and remediate, and your patching, testing, and release procedures to get the patch tested and out to the machines that need it as quickly as possible.

"When these types of stories hit it makes me wonder: How many people are concerned about the effect of the zero day, and what does that say about the state of their networks?" Horan asked.

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